1070-4272/03/7612-1920 $25.00 C 2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 12, 2003, pp. 1920!1924. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 12, 2003,
Original Russian Text Copyright + 2003 by Kasenov, Tukhmetova, Turmukhambetov, Kasenova, Mustafin, Adekenov, Krichevskii.
OF SYSTEMS AND PROCESSES
Thermochemistry of Lappaconitine Hydrobromide
and Its Analogues
B. K. Kasenov, Zh. K. Tukhmetova, A. Zh. Turmukhambetov, Sh. B. Kasenova,
E. S. Mustafin, S. M. Adekenov, and L. A. Krichevskii
Institute of Phytochemistry, Ministry of Education and Science of the Republic of Kazakhstan,
Received July 15, 2003
Abstract-Isothermal calorimetry was applied to study the heats of dissolution of lappaconitine hydro-
bromide at varied dilution. The data obtained were used to calculate the standard enthalpy of dissolution
. HBr in an infinitely diluted (standard) aqueous solution. The heats of combustion and
melting of C
. HBr were calculated using approximate methods. A combination of experimental
and calculation techniques was used to find the standard heats of formation of lappaconitine hydrobromide
and its 33 analogues.
Studying the thermochemical and thermodynamic
properties of alkaloids is of certain theoretical and
practical interest for directed synthesis of these com-
pounds with prescribed properties.
The alkaloid lappaconitine is an ester of triatomic
amino alcohol lappaconine and N-acetylanthranilic
acid; the structural formula of lappaconitine hydro-
bromide (allapinine) is given below :
It should be emphasized that, until now, neither
experimental nor estimated values of the thermochem-
ical and thermodynamic constants of this theoretically
and practically important alkaloid and its derivatives
are available in the literature.
In view of the aforesaid, the aim of this study
was to analyze experimentally the thermochemical
properties of lappaconitine hydrobromide and to use
the data obtained to find, by combining calculation
procedures, the standard enthalpies of formation of
. HBr and its analogues.
The enthalpy of dissolution of lappaconitine hy-
. HBr in water was stud-
ied calorimetrically under isothermal conditions on
a DAK-1-1A calorimeter. The theory of, and proce-
dure for a calorimetric study were described in detail
in . The DAK-1-1A commercial differential au-
tomated calorimeter has the following main technical
characteristics: working temperatures 253200oC, car-
tridge volume 8 cm
, error in measuring heat release
energy <20 mW. The calorimeter measures the integral
heat flux outgoing from the calorimetric cartridge, in
which a substance is being dissolved, through the dif-
ferentially connected thermocouples and the massive
central unit of the microcalorimeter. The rated error
in determining the heat effects is +2.0%.
The experimental errors and the uniformity of var-
iance in determining the heat effects were calculated
using the Student and Bartlett criteria.
The heat of combustion of lappaconitine hydro-
bromide was calculated using the Karas and Frost
methods , and the heat of fusion was found from
an empirical equation recommended in .
The values of D
for analogues of C
HBr were calculated using the system of enthalpy in-
crements for anions [9, 10].